High-efficiency duty-cycle controlled fullbridge converter for ultracapacitor chargers

This study proposes a high-efficiency duty-cycle controlled full-bridge dc-dc converter for ultracapacitor chargers. By the asymmetric duty-cycle control, the proposed converter achieves zero-voltage switching of power switches without circulating currents. It reduces the output current ripple by the current-doubler rectifier. A control strategy is suggested for charging ultracapacitors. A constant current and constant voltage charging is performed. The proposed converter achieves a higher efficiency compared with the conventional phase-shift controlled full-bridge converter. The performance of the proposed converter is evaluated by experimental results for a 30 F ultracapacitor bank.